Both quality assurance and quality control in a construction project are aimed at ensuring quality of the final product - the building. Even though they are critical parts of a construction project's quality management program, professionals often use the two terms interchangeably or listed together as QA/QC in construction consulting companies’ service offerings.
However, Quality Assurance and Quality Control are distinctly different activities.
Why should anyone care about the difference? There are several reasons why.
Understanding the difference between QA and QC helps clarify the communication between project owners, contractors and other stakeholders. A good understanding helps project owners and managers build the right team of internal and third party construction quality consultants to meet the project's quality goals. Conversely, a poor understanding can lead to decisions to forgo one or the other, increasing the risks of construction defects and other claims down the road.
Quality Assurance (QA) is a set of planned and systematic activities which are laid out before a building project starts. The aim of this activity plan is to give confidence that quality requirements will be fulfilled. We can put it simply, like this:
Quality Assurance is planning to do the right things at the right time and the right way.
Quality Control (QC) are observation techniques and activities which aim to identify whether the final product actually fulfills customer requirements. Quality Control also identifies the need for corrective measures. In other, simpler, words:
Quality Control monitors work as it happens and ensures that the results satisfy the requirements specified.
Quality Assurance is about a plan. It is carried out before the construction project starts. Quality Assurance is a process that manages for quality. QA lists the processes, standards and policies that need to be carried out and ensures they are known to the people who need to know them.
For example, when working on a building's foundation, quality assurance is the process of having someone check the rebar & forms, submitting issues that need fixing to a private website, and tracking that they're fixed before concrete pouring begins.
The key elements of Quality Control are observation and activity. Even when you have the best plan and system in place (that’s what Quality Assurance does), you still need to monitor the work as it occurs to make sure the results are what you expect them to be. In plain-speak, QC is the inspection of the craftsmanship on a construction project. Quality Control verifies the quality of the output.
Going back to the foundation example, quality control will be the inspector visiting the construction site, checking that rebar is suspended at the right height, tied appropriately, and that inside the forms are free of debris.
Both QA and QC are valuable practices to help ensure quality. It pays to determine what exactly quality is. Quality is a measure of excellence in how well a product or service meets the client and end-user's requirements and needs.
In new building construction, the end product is the completed structure and the surrounding property it sits on. A quality building is free from defects and significant shortcomings. It is the result of a process that adheres to the local building code, measurable and verifiable standards, and achieves its performance goals and requirements. Ensuring quality in a project is a standard goal for construction professionals for many reasons, one of which is that helps manage the risks against unwanted results, like claims.
Quality Assurance and Quality Control are different, but complementary part of a larger concept – Quality Management. Achieving success in a building project requires both QA and QC. If either QA or QC are left out, it becomes near impossible to produce an effective construction quality program.
If you only lay out plans that define processes and procedures to be carried out (QA) but they aren't followed by anybody, its become little more than a paper making exercise. Those plans may be great however poor execution will lead to lots of rework, change orders, and mistakes slipping through, only to later become construction defects.
On the other hand, if your inspectors conduct testing and observations to check the quality (QC) without a plan, you can miss the whole picture. The project can end up with inspection gaps or lack of follow-ups, mistakes can go undocumented and unaddressed. The project managers wouldn’t be able to see underlying greater problems that needed timely addressing – creating failures to improve the general way of delivering the product.